There is increasing evidence that people of color are disproportionately exposed to numerous environmental hazards, including hazardous air pollutants such as polycyclic aromatic hydrocarbons (PAH) and environmental tobacco smoke (ETS). The Washington Heights and Harlem neighborhoods in Manhattan are typical of other Hispanic and African American communities in that they are located in a large sprawling metropolitan area characterized by elevated air pollution. The incidence of low birth weight is higher among African Americans living in Central Harlem and Hispanics living in Washington Heights than in Caucasians in the U.S. Cancer rates are also higher in African Americans than in Caucasians. Environmental risks to the developing infant are of particular concern, given the likelihood of increased susceptibility during this period. A molecular epidemiologic cohort study of African American and Hispanic mothers and newborns is proposed to investigate the role of PAH and ETS in procarcinogenic and developmental damage. A combination of personal monitoring, questionnaire and biomarkers in peripheral blood will be used to quantify individual exposure to the toxicants of concern. The biomarkers include PAH-DNA adducts in white blood cells (an indicator of PAH exposure and procarcinogenic genetic damage) and plasma cotinine (a metabolite of nicotine and internal dosimeter of ETS). Measures of development will be assessed in the infants at birth and at 6 and 12 months. The proposal is responsive to concerns about environmental justice and to the recommendation of the National Research Council that risk assessment and public health policy pay special attention to the protection of young infants and children.